Various methods, such as adsorption, membrane separation, precipitation, biological decomposition, and chemical decomposition, are applied to purify contaminated water. It is very common that positive ion contaminants, such as Cu2+, is Pb2+, Zn2+, Ni2+, and Cd2+, and negative ion contaminants, AsO43−, AsO33−, Cr2O72—, PO43−, F−, and NO3− are mixed in contaminated water, such as industry waste water or mine drainage. An existing technique for purifying contaminated water containing both positive ion contaminants and negative ion contaminants is utilized by combining two or more techniques including a process of removing positive ion contaminants and a process of removing negative ion contaminants. Thus, existing contamination purifying methods use several techniques and thus their procedures are complicated and many costs are required.
Various adsorbents for removing positive or negative ion contaminants have been developed and are applied to sites. Methods of removing contaminants using adsorption are largely classified into a method of removing an adsorbent by mixing the adsorbent with contaminated water and then by adsorbing contaminants and a method of removing contaminants by allowing a column filled with an adsorbent to pass. An existing adsorbent has high adsorption performance with respect to positive or negative ions; however, an adsorbent having performance of simultaneously removing positive ions and negative ions is restrictive.
Also, when the adsorbent is mixed with contaminated water and is removed, the adsorbent is configured in the form of fine particles having a wide adsorption area so as to improve an adsorption force with respect to contaminants.
For example, activated carbon that is widely used in sites, is known as being capable of simultaneously removing positive ion contaminants and negative ion contaminants from waste water. Also, activated carbon has a large specific surface area and thus has high adsorption performance. However, it is difficult to separate and recover activated carbon after water treatment is completed.